When an incandescent lamp is dimmed, the color temperature drops turning the emitted light warmer with an increased reddish content. In contrast, white LED light sources have a fixed Correlated Color Temperature (CCT), such as 2700 K or 3000 K, which, when dimmed, do not change the CCT. Because a CCT of a light emitted by a lighting device is a combination of the lights emitted by different light sources of the lighting device, some LED lighting devices rely on multiple strings of LEDs, where some the strings of LEDs emit a cool light (e.g., 400 K or 5000 K) while the other one or more strings of LEDS emit a colored light or a warmer white light to make the combined light warmer (e.g. 2700 K or 3000 K). For example, an LED lighting device may include RED and Amber LEDs to shift the CCT of the light emitted by the lighting device along the Black Body Curve (BBC) in the direction of lower CCT. As another example, some LED lighting devices include an additional string of LEDs that emit a white light on the black body curve with a very low CCT that mimics a light from a dimmed incandescent lamp (e.g., 2000 K to 1600 K).
Some lighting devices rely on processor-based Pulse Width Modulation (PWM) circuitry to control current distribution among different strings of LEDs (e.g., a string that emits a cool light (e.g., 3000 K) and a string that emits a warm light (e.g., 1800 K)). However, achieving a desired precision in steering current among the strings of LEDs may be challenging, particularly at lower current levels when dimming is at max. Further, when the current provided by the driver is reduced for high dim levels, the processor may end up consuming a relatively large enough portion of the reduced current such that the light is prematurely turned off. Thus, a solution that enables CCT adjustment in correlation with dim level changes with high precision is desirable.